Vibration sensor

Abstract

In a vibration sensor for outputting, as vibration signals, variations of capacitance between a fixed electrode and a diaphragm 3 electrode opposed thereto, the diaphragm electrode 3 has slits 3 a formed in the same plate member to define a diaphragm portion 3 b positioned centrally to be vibrated and displace only by gravity, a fixed portion 3 c positioned peripherally, and elastic support portions 3 d for connecting the diaphragm portion 3 b to the fixed portion 3 c.

1 . A vibration sensor for outputting, as vibration signals, variations of capacitance between a fixed electrode and a diaphragm electrode opposed thereto, 
 wherein the diaphragm electrode has slits formed in the same plate member to define a diaphragm portion positioned centrally to be vibrated and displaced only by gravity, a fixed portion positioned peripherally, and elastic support portions for connecting the diaphragm portion to the fixed portion.    
   
   
       2 . A vibration sensor as defined in  claim 1 , wherein the plate member is made of one of stainless steel, tungsten, Ti·Cu alloy and Be·Cu alloy.  
   
   
       3 . A vibration sensor as defined in  claim 1 , wherein the plate member is 30 μm to 50 μm in thickness.  
   
   
       4 . A vibration sensor as defined in  claim 1 , wherein the diaphragm portion has a circular shape, and each of the elastic support portions is formed as an arcuate strip member with one end continuous with the diaphragm portion and the other end continuous with the fixed portion, a plurality of elastic support portions being arranged at equal intervals circumferentially of the diaphragm portion.  
   
   
       5 . A vibration sensor as defined in  claim 1 , wherein the elastic support portion is formed to have a beam shape for connecting a position of the diaphragm portion at an outer periphery thereof to the fixed portion adjacent said position of the diaphragm portion.